The experiments were performed on a Hewlett Packard LDI 1700XP time-of-flight mass spectrometer. Aqueous solutions of the glycopeptides from fetuin, ovalbumin, and rhodopsin were mixed with an aqueous 90% methanol solution of 100 mM 2,5-dihydroxy-benzoic acid (DHB), the MALDI matrix. Approximately 1 l of the sample/matrix mixture was placed on the probe tip and vacuum crystallized. The mass spectrum was recorded over a mass-to-charge (m/z) range of 1-2,500.